Refining and stabilizing petroleum wax



United States Patent 3,232,862 REFINING AND STABILIZING PETROLEUM WAX William B. Watson, Park Forest, Ill., and Herman R. Bentley, Hammond, Ind., assignors to Sinclair Research, Inc., Wilmington, DeL, a corporation of Delaware No Drawing. Filed Dec. 26, 1961, der. No. 162,197 6 Claims. (Cl. 208-27) This invention relates to a method for the production of high quality petroleum waxes suitable for food uses, such as the coating of paper for packaging food materials.

Processes for refining and stabilizing raw petroleum waxes such as slack wax and scale wax involving hydrofining and earth finishing treatments are known to the art. The partially refined waxes resulting from the hydrofining treatment are often of good color but have a relatively strong odor so that if the final wax product is to be marketed for food uses, it is ordinarily stabilized by an earth finishing process. Earth finishing processes, such as the percolation process and the contact process, are relatively expensive operations requiring the handling of large quantities of materials in semi-continuous operatiCiiiS. Consequently, there is a fid in the art for a more economical Wax refining process adaptable to continuous operations.

By the process of the present invention, raw petroleum waxes are subjected to a series of refining operations including hydrogenation and treating with an alkaline material such as an alkali metal hydroxide or carbonate to provide light colored, low odor Waxes suitable for food uses. Thus, in accordance with this invention, a raw petroleum wax is hydrogenated by passing it in admixture with hydrogen under elevated conditions of temperature and pressure into contact with a hydrogenation catalyst. The liquefied hydrogenated wax is then subjected to a treatment with an alkaline material, which can be an alkali metal carbonate or hydroxide, in an amount and for a time sufficient to produce a finished wax having a substantially reduced odor level.

Any raw wax stock derived from petroleum by conventional separation procedures can be employed in the process of this invention. Such raw wax stocks include slack waxes, scale waxes, sweat waxes, and block waxes, which are refined to yield parafiin or crystalline waxes, and p-etrolatums and petrolatum waxes, which are refined to yield microcrystalline waxes. The wax feed to the hydrogenation step advantageously has an oil content of no more than about 10 volume percent to minimize the amount of materials processed and preferably, if necessary, the raw petroleum Wax should be at least partially deoiled to an oil content of no more than about volume percent. Since hydrogenation can adversely soften the wax, advantageously the final deoiling should follow the hydrogenation step. In some cases, however, all of the deoiling can precede the hydrogenation step, the hydrogenation conditions beint controlled to yield a product having the required degree of hardness. The steps of deoiling and hydrogenation, however, can be interchanged as long as the treatment with an alkaline material is the final step.

The raw petroleum waxes can be deoiled by a conventional sweating procedure or by a conventional solvent deoiling process. In the former, the wax, after initial separation from petroleum oil by filtration at reduced temperatures, is held in perforated sweating pans and is exposed in solid form to a gradually rising temperature whereby the oily constituents of the wax tend to separate,

leaving the deoiled wax in the sweating pans. In the solvent deoiling processes, the wax which can be raw wax or a semi-refined wax from a sweating process, is recrystallized from solvents such as ketones, benzene-ketone mixtures, chlorinated solvents, hydrocarbons, and the like. The recrystallization is conventional and includes admixing the wax and solvent and passing the mixture through a chiller and then to a filter to remove wax and distilling the solvent from the dewaxed oil. Generally about 100 to 600 percent of solvent based on wax is sufficient and filter temperatures of 0 to 30 F. are used. It is recognized that solvent deoiling techniques can replace or complement sweating techniques used in the initial and/ or final deoilin g steps.

Although the conditions of hydrogenation can be varied considerably, generally the temperature used is within the range from about 550 to 750 F. and the pressure is within the range from about 1000 to 3500 p.s.i.g. The weight hourly space velocity is generally within the range from about 0.5 to 10 and the hydrogen to Wax ratio is within the range from about 200 to 5000 standard cubic feet of hydrogen per barrel of wax.

Any of the catalysts conventionally employed in the hydrogenation of heavy petroleum oils can be utilized in accordance with the present process. Examples of suitable catalytic ingredients are molybdenum, tungsten, vanadium, chromium, cobalt, nickel, iron and tin and their oxides and sulfides. Mixtures of these materials or compounds of two or more of the oxides can be employed. For example, mixtures or compounds of the iron group metal oxides or sulfides with the oxides or sulfides of Group VI left column of the Periodic Table constitute very satisfactory catalysts. Examples of such mixtures or compounds are nickel molybdate, tungstate or chromate (or thiomolybdate, thiotungstate or thiochromate) or mixtures of nickel oxide with molybdenum, tungsten or chromium oxides. As the art is aware and as the specific examples illustrate, these catalytic ingredients are generally employed while disposed upon a suitable carrier or" the solid refractory type. Advantageously the catalyst is cobalt rfiolybdate supported on alumina. Such preferred catalysts can be prepared by the method described in US. Patent 2,93 8,002 issued May 24, 1960, to Carl D. Keith et al.

If necessary, the hydrogenated Wax is deoiled to the required degree of hardness by conventional sweating and/ or solvent deoiling techniques and the deoiled hydrogenated liquefied wax is treated with an alkaline material which can be an alkali metal carbonate, such as sodium or potassium carbonate, or an alkali metal hydroxide, such as sodium or potassium hydroxide, in an amount and for a time sufficient to produce a finished wax having a substantially reduced odor level. The wax is in liquid phase to provide good contact and is generall maintained at a temperature of about 10 to F. above its melting point. The alkaline material, if an alkali metal carbonate, is advantageously in aqueous solution of a concentration of about 8 to 18 Baum, and if an alkali metal hydroxide, is advantageously in aqueous solution of a concentration of about 10 to 40 Baum. The aqueous alkaline solution is contacted with the molten wax, advantageously continuously, in an amount of about 5 to 50 volumes of solution per hundred volumes of wax for a period of about 5 to 60 minutes. The mixture is then steamed and allowed to settle in two layers with the upper layer being finished marketable wax.

The process of this invention is further illustrated by the following specific examples.

Example 1 Petrolatum A produced by dewaxing a Mid-Continent bright stock lubricating oil, was partially deoiled in a conventional, continuous solvent dewaxing-d-eoiling plant. The solvent consisted of a 50/50 volume percent blend of methyl ethyl ketone and toluene, and dilution solvent to petrolatum ratio was 6 to 1 on a volume basis. Filtering temperature was +30 F., and Wash solvent to petro- 3 latum ratio was 4.6 to 1. Yield of deoiled wax, Wax B, was 53.6 volume percent. Properties of Petrolatum A and Wax B are given below:

F. filtering temperature. Yield of wax, Wax G, was 64.2 volume percent.

Wax G was hydrogenated at 1500 p.s.i.g., 700 F., 1.0 WHSV, and a hydrogen rate of 2500 standard cubic feet Test ASTM Pet). Wax]; 5 per barrel over the catalyst of Example 1. Yield of hy- Designation lfltumA drogenated wax, Wax H, was 99.9 volume percent.

Wax H was deoiled with a 50/ 50 volume percent blend Gravity, 13487-55 of methyl ethyl ketone and toluene, 10 to l dilution sol- 0. o s l i r ifii fiil'. D 721 561 5 98 if; vent ratio, 5:1 wash solvent ratio, and +30 F. filtering Needle Penetration at 77 F 88 20 Melting Point (Pet), 0 F D 12H9 D 160.2 168.2 10 temoperature. Y1eld of deoiled wax, Parafiin Wax I, was UV Absorptivity at 290 mmu, its-50 0, 78. volume percent. Parafiin Wax I had a strong, un-

l./g.-em. acceptable odor.

Paraffin Wax J was admixed at 180 F. with 10 volume W X B Was hydrog nate t 1 P g percent based on wax of 35.8 Baum sodium hydroxide WHSV, and a hydrogen rate of 2500 standard cubic feet 15 solution. The mixture was stirred for minutes, steamed per barrel over a cobalt molybdena on alumina catalyst for ten minutes, and allowed to settle into two layers. (2.7% CoO, 11.9% M00 Yield on hydrogenated The upper wax layer, Paraffin Wax K, was withdrawn wax, Wax C, was 99.7 volume percent. through a blotter press. Paraffin Wax K has a faint sweet Wax C was deoiled using a batch procedure with a odor and meets all requirements for wax for packaging 50/50 volume percent blend of methyl ethyl ketone and 20 foods. toluene, 10 tol dilution solvent ratio, 5 to 1 wash solvent Tests on the various waxes described in Example 2 are ratio, and +50 F. filtering temperature. Yield of the listed in TableIbelow:

TABLE I Test ASTM Desig- Slack Wax G Wax H Paralfin Paraflin nation Wax F WaxJ WaxK Gravity, API D-287-55 39.8 41.4 41.4 41.7 41.7 on Content, percent D72156T 10. 2 3. 14 4. 7s 0. 00 0.00 Saybolt Color 13-16 30+ 30+ Needle Penetration at 77 F-.. 31 14 14 Melting Point (Parafiin) F- 135.8 133. 6 141. s 141. s Carbonizable Substances Fail Fail Pass Pass Odor Bad Good deoiled wax, Microcrystalline Wax D, was 78.9 volume percent. This wax was in all physical respects an excellent microcrystalline wax of good color and hardness and low oil and aromatic content, but it had a strong penetrating odor unsuitable for packaging foods.

Properties of Wax C and Microcrystalline Wax D are given below:

Micro- Test ASTM Desig- Wax 0 crystalnation line Wax D Gravity, API 35. 1 35. 7 Oil Content, peree11t D721-56T 2. 21 0. 00 ASTM Color D1500-58T L0. 5 L0. 5 Needle Penetration at 77 F. D132157T 25 12 Melting Point (Pen), F 13-127-49 168. 8 170. 8 UY/ Absorptivity at 290 mmu, ES-50 0. 084 0. 047

Example 2 Similarly a slack wax, Slack Wax F, derived from a lubricating oil distillate fraction was partially deoiled, hydrogenated, further deoiled, and caustic washed to yield a finished wax of excellent odor and color.

Slack Wax F was deoiled with a 50/ 50 volume percent blend of methyl ethyl ketone and toluene, a 6 to 1 dilution solvent ratio, a 4 to 1 wash solvent ratio, and +33 We claim:

1. In the production of petroleum waxes, the steps of hydrogenating a partially deoiled raw petroleum wax having an oil content of no more than about 10 volume percent by passing the raw petroleum wax in admixture with hydrogen at a temperature within the range from about 550 to 750 F., at a pressure within the range from about 1000 to 3500 p.s.i.g., at a weight hourly space velocity within the range from about 0.5 to 10 and employing a hydrogen-to-wax ratio within the range from about 200 to 5,000 standard cubic feet per barrel by contact with a hydrogenation catalyst consisting essentially of an iron group metal compound and a Group V1 metal compound, said compounds being selected from the group consisting of oxides and sulfides, on a solid refractory carrier to produce a hydrogenated wax, deoiling the hydrogenated wax and treating the deoiled, hydrogenated wax in liquid phase with an aqueous alkaline material selected from the class consisting of alkali metal hydroxides and alkali metal carbonates for about 5 to 60 minutes in an amount sufiicient to produce a finished wax having a substantially reduced odor level but with no substantial change in gravity, oil content, color, penetration and melting point.

2. The method of claim 1 wherein the wax is treated with aqueous alkaline material in anamount of about 5 to 50 volumes of material per hundred volumes of wax and at a temperature of about 10 to 75 F., above the melting point of the wax.

3. The method of claim 1 wherein the hydrogenation catalyst is cobalt molybdate supported on alumina.

4. The method of claim 3 wherein the raw petroleum wax is slack wax and wherein the alkaline material is aqueous sodium hydroxide.

5. The method of claim 3 wherein the raw deoiled petroleum wax is petrolatum and wherein the alkaline material is aqueous sodium carbonate.

6. The method of claim 2 wherein the treatment of 53) the deoiled hydrogenated want with an aqueous alkaline material includes steam stripping of the admixture of wax and alkaline material.

References Cited by the Examiner UNITED STATES PATENTS 2,075,871 4/1937 Smith 203-285 2,429,727 10/1947 Macke et a1. 208-27 2,956,001 16/1960 Spars et al. 20827 3,052,622 9/1962 Johnson et al. 20827 FOREIGN PATENTS 797,744 7/ 1958 Great Britain.

DELBERT E. GANTZ, Primary Examiner.

ALPHGNSO D. SULLIVAN, Examiner. 

1. IN THE PRODUCTION OF PETROLEUM WAXES, THE STEPS OF HYDROGENATING A PARTIALLY DEOILED RAW PETROLEUM WAXHAVING AN OIL CONTENT OF NO MORE THAN ABOUT 10 VOLUME PERCENT BY PASSING THE RAW PETROLEUM WAX IN ADMIXTURE WITH HYDROGEN AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 550* TO 750*F., AT A PRESSURE WITHIN THE RANGE FROM ABOUT 1000 TO 3500 P.S.I.G., AT A WEIGHT HOURLY SPACE VELOCITY WITHIN THE RANGE FROM ABOUT 0.5 TO 10 AND EMPLOYING A HYDROGEN-TO-WAX RATION WITHIN THE RANGE FROM ABOUT 200 TO 5,000 STANDARD CUBIC FEET PER BARREL BY CONTACT WITH A HYDROGENATION CATALYST CONSISTING ESSENTIALLY OF AN IRON GROUP METAL COMPOUND AND A GROUP VI METAL COMPOUND, SAID COMPOUNDS BEING SELECTED FROM THE GROUP CONSISTING OF OXIDES AND SULFIDES, ON A SOLID REFRACTORY CARRIER TO PRODUCE A HYDROGENATED WAX, DEOILING THE HYDROGENATED WAX AND TREATING THE DEOILED, HYDROGENATED WAX IN LIQUID PHASE WITH AN AQUEOUS ALKALINE MATERIAL SELECTED FROM THE CLASS CONSISTING OF ALKALI METAL HYDROXIDES AND ALKALI METAL CARBONATES FOR ABOUT 5 TO 60 MINUTES IN AN AMOUNT SUFFICIENT TO PRODUCE A FINISHED WAX HAVING A SUBSTANTIALLY REDUCED ODOR LEVEL BUT WITH NO SUBSTANTIAL CHANGE IN GRAVITY, OIL CONTENT, COLOR, PENETRATION AND MELTING POINT. 